Control device and control method for extraction device

ABSTRACT

The purpose of the present invention is to provide a control device which is for an extraction device, and is capable of estimating the total amount of air intrusion more accurately and optimizing the operation of the extraction device. A control device (7) that controls an extraction device (6) provided in a refrigerator (1) is provided with: an estimating unit that estimates the total amount of air intruding into the refrigerator (1); a determining unit that determines whether or not the total amount of air intrusion is equal to or greater than a preset allowable value; an activation control unit (6) that determines an activation duration time of the extraction device (6) on the basis of the total amount of air intrusion when the total amount of air intrusion is equal to or greater than the allowable value, and that activates the extraction device (6) for the activation duration time; an exhaust air amount calculation unit that calculates an amount of exhaust air that is the amount of air actually exhausted by the extraction device (6); and a correction unit that corrects at least one among the total amount of air intrusion and the activation duration time when the difference between the total amount of air intrusion and the amount of exhaust air is equal to or larger than a predetermined amount.

TECHNICAL FIELD

The present invention relates to a chiller, and particularly to acontrol device and a control method for an extraction device.

BACKGROUND ART

A chiller that adopts a low-pressure refrigerant has a possibility thata non-condensable gas (mainly air) infiltrates into the chiller andstays in a condenser in a case where in particular sealabilitydeteriorates since the inside of the chiller comes under a negativepressure according to an operation condition. In this state, acondensation pressure rises due to the non-condensable gas, and therebythere is a concern that the condenser does not operate normally. Forthis reason, in the related art, the non-condensable gas that hasentered the device is discharged into the atmosphere by the extractiondevice.

Due to amendments to a CFC collection and destruction law and EuropeanF-gas regulations, it is desirable for the chiller to use a low-GWPrefrigerant which is a low-pressure refrigerant. However, the low-GWPrefrigerant is easily decomposed by oxygen, and thus there is apossibility that byproducts affecting safe operation of the chiller isgenerated. In a case where a non-condensable gas has infiltrated in thechiller using the low-GWP refrigerant, there is a possibility that thelow-GWP refrigerant is decomposed and the operation of the chillerbecomes unstable. For this reason, in order to maintain the safeoperation of the chiller using the low-GWP refrigerant, it is necessaryto highly accurately estimate and appropriately extract the amount ofthe non-condensable gas in the device (total amount of infiltrated air).

PTL 1 discloses a method of estimating a total amount of infiltrated airinto a chiller according to a chiller structure and a pressure state andcontrolling the start of an extraction device based on the estimatedtotal amount of infiltrated air.

CITATION LIST Patent Literature

[PTL 1] Japanese Unexamined Patent Application Publication No.2016-65673

SUMMARY OF INVENTION Technical Problem

However, since the total amount of infiltrated air changes according tovarious conditions such as external environments including humidity andan outside temperature, it is difficult to highly accurately estimatethe total amount of infiltrated air. For this reason, under a situationwhere a possibility that a non-condensable gas infiltrates is low, alarge air infiltration amount is estimated and the extraction device isoperated uselessly in some cases.

In view of such circumstances, an object of the present invention is toprovide a control device and a control method for an extraction devicethat can more accurately estimate a total amount of infiltrated air andfurther optimize operation of the extraction device.

Solution to Problem

According to a first aspect of the present invention, there is provideda control device that controls an extraction device provided in achiller. The control device includes an estimating unit that estimates atotal air infiltration amount into the chiller, a determination unitthat determines whether or not the total air infiltration amount isequal to or larger than an allowable value set in advance, a startingcontrol unit that determines a starting continuation time of theextraction device based on the total air infiltration amount and startsthe extraction device for the starting continuation time in a case wherethe total air infiltration amount is equal to or larger than theallowable value, a discharge air amount calculating unit that calculatesa discharge air amount, which is an amount of air actually discharged bythe extraction device, and a correcting unit that corrects at least anyone of the total air infiltration amount and the starting continuationtime in a case where a difference between the total air infiltrationamount and the discharge air amount is equal to or larger than apredetermined amount.

According to the configuration, since the discharge air amount, which isthe amount of air actually extracted, is calculated, and at least anyone of the total amount of infiltrated air and the starting continuationtime of the extraction device is corrected with the use of thedischarged air amount, the total amount of infiltrated air can be moreaccurately corrected according to an actual operation status of thechiller. Since the starting continuation time of the extraction deviceis determined based on the total amount of infiltrated air, the totalamount of infiltrated air is indirectly corrected even in a case wherethe starting continuation time is corrected. That is, it is possible tomore accurately estimate the total amount of infiltrated air accordingto an operation status. For example, even in a case where a low-GWPrefrigerant is used as a refrigerant of the chiller, it is possible tomore accurately estimate the total amount of infiltrated air. Thus, morestable operation can be maintained.

In the control device, the correcting unit may correct at least any oneof the total amount of infiltrated air and the starting continuationtime by multiplying the total amount of infiltrated air or the startingcontinuation time by a correction constant according to the differencebetween the total amount of infiltrated air estimated by the estimatingunit and the discharge air amount.

According to the configuration, in a case where the difference betweenthe estimated total amount of infiltrated air and the actual dischargeair amount is large, correction can be performed with simple calculationof multiplying the air infiltration amount and/or the startingcontinuation time by the correction constant. For this reason,correction can be performed without a processing burden.

In the control device, the correction constant may be a value obtainedby dividing the discharge air amount by the total amount of infiltratedair.

According to the configuration, since correction can be performed withsimple calculation, correction can be performed without a processingburden.

In the control device, the chiller may be divided into a plurality ofsections, an air infiltration effect degree may be set for each of thesections, the estimating unit may estimate an air infiltration amountfor each of the sections and estimate the total amount of infiltratedair of the entire chiller from the estimated air infiltration amount ofeach of the sections, and the correcting unit may correct the airinfiltration amount for each of the sections according to the airinfiltration effect degree in a case of correcting the total amount ofinfiltrated air.

According to the configuration, since the air infiltration amount can becorrected for each section according to an air infiltration effectdegree, it is possible to perform highly accurate correction accordingto an operation state of the chiller and a structure of each section.Since the respective sections have configurations different from eachother, such as the number of couplings, the easiness of air infiltration(air infiltration effect degree) varies. For this reason, an airinfiltration amount of a section where air infiltrates easily can beeffectively corrected by performing correction according to an airinfiltration effect degree. For this reason, the total amount ofinfiltrated air can be more accurately estimated.

According to a second aspect of the present invention, there is provideda chiller that adopts a low-pressure low-GWP refrigerant. The chillerincludes an extraction device and the control device.

According to a third aspect of the present invention, there is provideda control method for an extraction device provided in a chiller. Thecontrol method includes an estimation step of estimating a total amountof infiltrated air into the chiller, a determination step of determiningwhether or not the total amount of infiltrated air is equal to or largerthan an allowable value set in advance, a starting control step ofdetermining a starting continuation time of the extraction device basedon the total amount of infiltrated air and starting the extractiondevice for the starting continuation time in a case where the totalamount of infiltrated air is equal to or larger than the allowablevalue, a discharge air amount calculation step of calculating adischarge air amount, which is an amount of air actually discharged bythe extraction device, and a correction step of correcting at least anyone of the total amount of infiltrated air and the starting continuationtime in a case where a difference between the total amount ofinfiltrated air and the discharge air amount is equal to or larger thana predetermined amount.

Advantageous Effects of Invention

According to the present invention, an effect of more accuratelyestimating a total amount of infiltrated air and optimizing theoperation of the extraction device can be achieved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing a schematic configuration of a chilleraccording to a first embodiment of the present invention.

FIG. 2 is a diagram showing functional blocks of a control deviceaccording to the first embodiment of the present invention.

FIG. 3 is a flowchart showing flow of a control method for an extractiondevice according to the first embodiment of the present invention.

FIG. 4 is a flowchart showing flow of a discharge air amount calculatingmethod executed by the control device according to the first embodimentof the present invention.

FIG. 5 is a flowchart showing flow of a correcting method executed bythe control device according to the first embodiment of the presentinvention.

FIG. 6 is a graph showing the amount of a non-condensable gas in acondenser of the chiller according to the first embodiment of thepresent invention.

FIG. 7 is a graph showing the amount of the non-condensable gas in theextraction device of the chiller according to the first embodiment ofthe present invention.

DESCRIPTION OF EMBODIMENTS First Embodiment

Hereinafter, a first embodiment of a control device and a control methodfor an extraction device according to the present invention will bedescribed with reference to the drawings.

FIG. 1 is a diagram showing a schematic configuration of a chiller 1according to the first embodiment of the present invention. As shown inFIG. 1, the chiller 1 according to the embodiment is a compressionchiller, and is configured to mainly include a compressor 2 thatcompresses a refrigerant, a condenser 3 that condenses thehigh-temperature and high-pressure gas refrigerant compressed by thecompressor 2, an expansion valve 4 that expands the liquid refrigerantfrom the condenser 3, an evaporator 5 that evaporates the liquidrefrigerant expanded by the expansion valve 4, an extraction device 6that discharges a non-condensable gas (mainly air) infiltrated in thechiller 1 to the atmosphere, and a control device 7 that control eachunit included in the chiller 1.

A low-GWP refrigerant, which is a low-pressure refrigerant, is adoptedas a refrigerant. Since the extraction device 6 according to theembodiment can accurately estimate the amount of the non-condensable gasinfiltrated in the device through correction to be described later, itis possible to use various refrigerants without being limited to thelow-GWP refrigerant.

The compressor 2 is, for example, a multi-state centrifugal compressordriven by a constant speed motor or a variable speed motor. Theextraction device 6 is connected to the condenser 3 by a pipe 8, and arefrigerant gas (including a non-condensable gas) from the condenser 3is led to an extraction tank 16 of the extraction device 6 through thepipe 8. The pipe 8 is provided with a valve 9 and a check valve 10,which are for controlling flowing and blocking of the refrigerant gas.As the control device 7 controls the opening and closing of the valve 9,the start and stop of the extraction device 6 are controlled. The checkvalve 10 prevents reverse flow of the refrigerant gas (including thenon-condensable gas) from the extraction tank 16 to the condenser 3 inthe extraction device 6.

The extraction device 6 includes, for example, the extraction tank 16that condenses the refrigerant gas (including the non-condensable gas)supplied through the pipe 8 by cooling the refrigerant gas with apeltier element and separates the refrigerant gas from thenon-condensable gas and a pump 11 that extracts the non-condensable gasaccumulated in the extraction tank 16 into the atmosphere. In theextraction tank 16, the non-condensable gas is discharged into theatmosphere, and the refrigerant gas separated from the non-condensablegas returns to the evaporator 5 through a pipe 13 by controlling a valve12. A configuration of the extraction device 6 is an example, and theextraction device is not limited to the configuration. Cooling with theuse of the peltier element is also an example of a cooling method forcondensing the refrigerant gas in the extraction tank 16, and thecooling method is not limited to the configuration.

The extraction tank 16 of the extraction device 6 is provided with apressure sensor 14 and a temperature sensor 15 in order to monitor astate of the non-condensable gas accumulated therein (the presence orabsence of the non-condensable gas or an accumulated amount).Measurement values from the sensors are transmitted to the controldevice 7, and are used in controlling the extraction device 6.

A configuration of the chiller 1 shown in FIG. 1 is an example, and thechiller is not limited to the configuration. For example, aconfiguration where an air heat exchanger is disposed instead of thecondenser 3 and heat is exchanged between the cooled outside air and arefrigerant may be adopted. The chiller 1 is not limited to a case ofhaving only a cooling function. For example, the chiller may have only aheating function or both of the cooling function and the heatingfunction.

The control device 7 has a function of controlling the compressor 2based on a measured value received from each of the sensors and a loadrate sent from a higher system and a function of controlling theextraction device 6.

The control device 7 includes, for example, a central processing unit(CPU), a memory such as a random access memory (RAM), and a computerreadable recording medium, which are not shown. A series of processesfor realizing a variety of functions to be described later are stored,for example, in a recording medium in a form of program. A variety offunctions to be described later are realized by the CPU reading theprogram from the RAM and executing processing and calculating ofinformation.

FIG. 2 is a functional block diagram showing a control function of theextraction device 6 which is selected from functions included in thecontrol device 7. As shown in FIG. 2, the control device 7 includes anestimating unit 21, a determination unit 22, a starting control unit 23,a storage unit 24, a discharge air amount calculating unit 25, and acorrecting unit 26.

The estimating unit 21 estimates a total amount of infiltrated air withthe use of an air infiltration effect degree indicating the easiness ofair infiltration determined from a structural aspect of the chiller 1and a function including a pressure as a parameter.

The air infiltration effect degree is, for example, an index indicatinghow large a gap, which has a possibility of allowing air (oxygen) toinfiltrate into the chiller 1, and is stored in the storage unit 24 inadvance. The air infiltration effect degree is determined by, forexample, a structure, a size, and the number of couplings that connect apipe. In consideration of a case where air infiltrates by permeating aresin material, an air infiltration effect degree may be set by addinginformation of the resin material.

In the embodiment, the chiller 1 is divided into a plurality ofsections, and an air infiltration effect degree is set for each section.

Herein, it is possible for the chiller to be divided into sections asappropriate. For example, division into sections may be performed suchthat places showing the same tendency become one section from aperspective of whether or not a negative pressure is likely to be causedaccording to an operation condition (for example, whether the chiller isbeing operated or stopped) and a winter season or a summer season. Forexample, the vicinity of the evaporator 5 is likely to come under thenegative pressure in the summer season, and a place other than arefueling system is likely to come under the negative pressure when thechiller is being operated or stopped in the winter season. Based on sucha tendency, for example, the vicinity of the evaporator 5 may bedetermined as one section. As for places other than the vicinity of theevaporator, for example, each of the vicinity of the compressor 2 andthe vicinity of the condenser 3 may be determined as one section.

The estimating unit 21 estimates an air infiltration amount for eachsection, for example, with the use of an air infiltration effect degreeset for each section, a pressure of each section, and the atmosphericpressure. Specifically, in a case where a pressure of a section ishigher than the atmospheric pressure, that is, in a case of a positivepressure, an air infiltration amount is zero. On the other hand, in acase where a pressure of a section is lower than the atmosphericpressure, that is, in a case of the negative pressure, a value obtainedby multiplying the 1/2 power of a differential pressure between thepressure and the atmospheric pressure by an air infiltration effectdegree is estimated as an air infiltration amount. When expressed into aformula, Expression (1) and Expression (2) below are obtained.

$\begin{matrix}{{{In}\mspace{14mu} a\mspace{14mu} {case}\mspace{14mu} {of}}{{{P(s)} - {Pat}} \geqq 0\left( {{in}\mspace{14mu} a\mspace{14mu} {case}\mspace{14mu} {of}\mspace{14mu} a\mspace{14mu} {positive}\mspace{14mu} {pressure}} \right)}{{M(s)} = 0}} & (1) \\{{{In}\mspace{14mu} a\mspace{14mu} {case}\mspace{14mu} {of}}{{{P(s)} - {Pat}} < \left( {{in}\mspace{14mu} a\mspace{14mu} {case}\mspace{14mu} {of}\mspace{14mu} a\mspace{14mu} {negative}\mspace{14mu} {pressure}} \right)}\begin{matrix}{{M(s)} = {{E(s)} \times {f\left( {{P(s)},{Pat}} \right)}}} \\{= {{E(s)} \times \sqrt{\;}{{{P(s)} - {Pat}}}}}\end{matrix}} & (2)\end{matrix}$

In Expression (1) and Expression (2), P(s) is a pressure [Pa(abs)] of asection s, Pat is the atmospheric pressure [Pa(abs)], M(s) is an airinfiltration amount [m³] of the section s, and E(s) is an airinfiltration effect degree [m³/Pa] of the section s. Without beinglimited to [m³] described above, for example, kg and mol may be used asthe unit of an air infiltration amount.

The air infiltration amount M(s) of the section s indicates the amountof air estimated to be infiltrated in the section s per unit time (perone control cycle) in a state of a pressure of the section s and theatmospheric pressure.

When the air infiltration amount M(s) is estimated for each section insuch a manner, the correcting unit 26 corrects the air infiltrationamount M(s), and thereby an air infiltration amount Ma(s) is calculated.Then, the estimating unit 21 adds a value obtained by adding up the airinfiltration amounts Ma(s) of the sections (an air infiltration amountMs(s)) to a previously integrated value of air infiltration amounts, tocalculate an integrated value of air infiltration amounts, that is, atotal of the air infiltration amounts of the entire chiller 1 at thecurrent time point (hereinafter, referred to as a “total amount ofinfiltrated air”). A formula thereof is Expression (3) below.

M(t)=M(t−1)+ΣMa(s)   (3)

In Expression (3), M(t) is a total amount of infiltrated air, M(t−1) isa previously integrated value of air infiltration amounts, and ΣMa(s) isa total value of air infiltration amounts for sections calculated thistime.

The determination unit 22 determines whether or not the total amount ofinfiltrated air M(t) estimated by the estimating unit 21 is equal to orlarger than an allowable value Mc set in advance.

The allowable value Mc is set, for example, based on a refrigerantchemical stability test and operation results. For example, a totalamount of infiltrated air, at which decomposition of a refrigerantoccurs, or a total amount of infiltrated air, at which safe operation ofthe chiller 1 is not inhibited, is acquired based on tests and operationresults, and the allowable value is set to a value smaller than thetotal amount of infiltrated air.

Herein, it is necessary for the unit of the allowable value Mc and theunit of a total amount of infiltrated air are consistent with eachother. For example, in a case where the unit of an allowable value is[mol] and the unit of a total amount of infiltrated air is other than[mol], the unit of the total amount of infiltrated air may be convertedto the unit of the allowable value [mol], and the total amount ofinfiltrated air after conversion and the allowable value may be comparedwith each other.

In a case where the total amount of infiltrated air M(t) is equal to orlarger than the allowable value Mc, the starting control unit 23 startsthe extraction device 6. For example, the starting control unit 23 opensthe valve 9 provided in the pipe 8 to start the extraction device 6. Astarting continuation time of the extraction device 6 is determined atany time according to a ratio of the total amount of infiltrated airM(t) of the entire chiller 1 to a chiller capacity.

In a case where a starting continuation time is determined at any timeaccording to a ratio of the total amount of infiltrated air M(t) of theentire chiller 1 to a chiller capacity, for example, Expression (4)below may be used.

tc=f[Vnc/Vc]  (4)

Vnc=M(t)+α  (5)

In Expression (4), tc is a starting continuation time [s] of theextraction device 6, and Vnc is the volume [m³] of a gas to be extractedand is calculated through Expression (5). Vc is an in-chiller volume[m³]. In Expression (5), the volume of a gas to be extracted is setslightly larger than the actual total amount of infiltrated air M(t) byadding a predetermined margin α to the total amount of infiltrated airM(t), and a margin is given to a starting continuation time to becalculated.

The starting continuation time tc of the extraction device 6 may becalculated through Expression (6) below in which the volume of a gas tobe extracted and a pulling capacity of the extraction device 6 areparameters.

tc=f[Vnc/va]  (6)

In Expression (6), va is a pulling capacity [m³/s] of the extractiondevice 6.

In a case where a total amount of infiltrated air is smaller than anallowable value, the starting control unit 23 does not start theextraction device 6.

Information to be referred in the processing of the estimating unit 21and the determination unit 22 described above is stored in advance inthe storage unit 24. For example, in addition to the air infiltrationeffect degree E(s) of each section and the allowable value Mc, aconstant included in each of Expressions (1)-(6) is registered inadvance. A table, in which a difference between the estimated totalamount of infiltrated air M(t) and a discharge air amount Md(t) and acorrection constant c are set to correspond to each other, is stored inthe storage unit 24. In a case where the total amount of infiltrated airM(t) is smaller than the discharge air amount Md(t), a correctionconstant is set to a value larger than 1. In a case where the totalamount of infiltrated air M(t) is larger than the discharge air amountMd(t), the correction constant c is set to a value smaller than 1. Thecorrection constant c is set according to a difference between theestimated total amount of infiltrated air M(t) and the discharge airamount Md(t), and is, for example, a value obtained by dividing thedischarge air amount Md(t) by the total amount of infiltrated air M(t).Even in a case where the correction constant c is not stored as a tablein the storage unit 24, a calculation formula may be stored to calculatethe correction constant at the time of correction.

The discharge air amount calculating unit 25 calculates the dischargeair amount Md(t), which is the amount of air actually extracted by theextraction device 6. When the extraction device 6 is actually operated,a non-condensable gas accumulates in the extraction tank 16 of theextraction device 6. Then, in a case where the non-condensable gasaccumulated in the extraction tank 16 reaches a predetermined amount setin advance (a one-time discharge amount D1), the valve 9 is closed tostop supplying a refrigerant gas from the condenser 3, and the pump 11provided in the extraction tank 16 is operated to discharge thenon-condensable gas into the atmosphere. When the discharge of thenon-condensable gas is completed, the valve 9 is opened again, andthereby the non-condensable gas accumulates in the extraction tank 16.Thus, the discharging operation described above is repeated until thedischarge of the non-condensable gas is completed. The dischargingoperation is executed one time or a plurality of times according to theamount of the non-condensable gas actually accumulated in the chiller 1for the set starting continuation time. Since the discharging operationis executed one time or a plurality of times for the startingcontinuation time of the extraction device 6, the discharge air amountMd(t), which is the amount of actually discharged air, can be calculatedby measuring the one-time discharge amount D1 and the number of times nat which the discharging operation is executed.

The one-time discharge amount D1 is determined based on the capacity ofthe extraction device 6 (mainly the extraction tank 16). That is, when anon-condensable gas corresponding to the capacity of the extraction tank16 is accumulated in the extraction device 6 (when the extraction tank16 is full of the non-condensable gas), the accumulated non-condensablegas is discharged. In a case of discharging the non-condensable gasaccumulated in the chiller 1 in a short period of time, it is preferableto use the extraction tank 16 having a large capacity in order toincrease the one-time discharge amount. In a case of more accuratelycalculating a discharge air amount, which is the amount of air actuallyextracted, it is preferable to decrease the one-time discharge amountand enhance an estimated resolving power of the discharge air amountMd(t). In this case, the extraction tank 16 having a small capacity maybe used.

The one-time discharge amount D1 may be determined at random with thecapacity of the extraction device 6 (mainly the extraction tank 16) setas an upper limit. In this case, the amount of the non-condensable gasin the extraction tank 16 is estimated by the pressure sensor 14 and thetemperature sensor 15, which are provided in the extraction device 6,and the estimated amount of the non-condensable gas and thepredetermined amount which is determined at random (the one-timedischarge amount D1) may be compared with each other.

In a case where a difference between the estimated total amount ofinfiltrated air M(t) and the discharge air amount Md(t) is equal to orlarger than a predetermined amount β, the correcting unit 26 corrects atleast any one of the estimated total amount of infiltrated air M(t) anda starting continuation time. For this reason, the correcting unit 26includes a correction necessity determination unit 31, a correctionconstant updating unit 32, and a correction executing unit 33. A case ofcorrecting the total amount of infiltrated air M(t) in the embodimentwill be described. The correction of the starting continuation time willbe described in a modification example below.

The correction necessity determination unit 31 determines whether or notit is necessary to correct the total amount of infiltrated air M(t) bydetermining whether or not a difference between the estimated totalamount of infiltrated air M(t) and the discharge air amount Md(t) isequal to or larger than the predetermined amount β. As will be describedlater, in a case where it is necessary to correct the total amount ofinfiltrated air M(t), the correction constant c for correcting theestimated air infiltration amount M(s) of each section is updated, andconsequently the total amount of infiltrated air M(t) is corrected. Thepredetermined amount β used by the correction necessity determinationunit 31 is set within a range of an error, which is allowed for thedischarge air amount, of the estimated total amount of infiltrated airM(t).

The correction constant updating unit 32 updates the correction constantin a case where the correction necessity determination unit 31determines that the difference between the estimated total amount ofinfiltrated air M(t) and the discharge air amount Md(t) is equal to orlarger than the predetermined amount β. The correction constant is setto 1 as an initial set value, and the correction constant is updatedeach time the correction necessity determination unit 31 determines thatit is necessary to correct the total amount of infiltrated air M(t).Specifically, in a case where it is determined that it is necessary tocorrect the total amount of infiltrated air M(t), the correctionconstant updating unit 32 reads a correction constant according to thedifference between the estimated total amount of infiltrated air M(t)and the discharge air amount Md(t) from the storage unit 24, andperforms update by multiplying a correction constant which is set upuntil then by the read correction constant. For example, in a case wherea correction constant of 1.1 is read from the storage unit 24 by thecorrection constant updating unit 32 in a state where the correctionconstant is set to 1.2, the correction constant is updated to a newcorrection constant through 1.2×1.1=1.32. The correction constant isupdated by being multiplied by a new correction constant each time it isdetermined that it is necessary to correct the total amount ofinfiltrated air M(t).

The correction executing unit 33 calculates the air infiltration amountMa(s) by multiplying the air infiltration amount M(s) of each sectionestimated by the estimating unit 21 by the correction constant. Then,the estimating unit 21 calculates the total amount of infiltrated airM(t) with the use of the air infiltration amount Ma(s) calculated by thecorrection executing unit 33.

Next, a control method for the extraction device 6 by the control device7 described above will be described with reference to FIG. 3. Thecorrection constant c is set to 1 as an initial value. In a case wherethe correction constant is updated by the correcting unit 26, theupdated correction constant c is used.

First, measurement values of the pressure P(s) of each section and theatmospheric pressure Pat are acquired from a variety of sensors (forexample, the pressure sensor and the temperature sensor (not shown inFIG. 1)) provided in the chiller 1 and near the chiller 1 (S301).

Next, the air infiltration amount M(s) of each section is calculatedwith the use of the pressure P(s) of each section and the atmosphericpressure Pat (S302).

Next, the air infiltration amount M(s) estimated for each section iscorrected (S303). Specifically, the air infiltration amount Ma(s) iscalculated by multiplying the air infiltration amount M(s) by thecorrection constant. Since the correction constant c is set to 1 as aninitial value, M(s)=Ma(s) is satisfied in a case where the correctionconstant is not updated. In a case where the correction constant isupdated, the updated correction constant (≠1) is used, and thusM(s)≠Ma(s) is satisfied.

Next, the total amount of infiltrated air M(t) is calculated by addingthe value ΣMa(s) obtained by adding the air infiltration amounts Ma(s)of respective sections to the previously integrated value M(t−1) of airinfiltration amounts (S304).

Next, whether or not the total amount of infiltrated air M(t) is equalto or larger than the allowable value Mc is determined (S305). Herein,in a case where the units of both of the total amount of infiltrated airand the allowable value do not match each other, the total amount ofinfiltrated air and the allowable value are compared with each otherafter performing processing of converting one unit to match the otherunit.

In a case where the total amount of infiltrated air M(t) is equal to orlarger than the allowable value Mc (determination of YES in S305) inS305, a starting continuation time is calculated based on the totalamount of infiltrated air M(t) (S306). Then, the extraction device 6 isstarted (S307). Next, whether or not the starting continuation time haselapsed is determined (S308). In a case where the starting continuationtime has elapsed, the extraction device 6 is stopped (S309).

Next, the previously integrated value M(t−1) of air infiltration amountsis set to zero (S310).

On the other hand, in a case where the total amount of infiltrated airM(t) is smaller than the allowable value Mc in S305, the total amount ofinfiltrated air M(t) calculated this time is set to the previouslyintegrated value M(t−1) of air infiltration amounts (S311).

The processing is continuously performed at fixed time intervals, forexample, regardless of the fact that the chiller 1 is being operated andbeing stopped.

Next, a discharge air amount calculating method for the extractiondevice 6 by the control device 7 described above will be described withreference to FIG. 4.

In a flowchart shown in FIG. 4, an operation starts when the extractiondevice 6 is started by the starting control unit 23.

First, when the extraction device 6 is started by the starting controlunit 23, the number of times of discharging operation n=0 is set (S401).

Next, in a case where whether or not the starting continuation time haselapsed is determined (S402) and the starting continuation time has notelapsed (determination of NO in S402), whether or not the dischargingoperation is performed by the extraction device 6 is determined (S403).In a case where it is determined that the discharging operation is notperformed (determination of NO in S403), whether or not the startingcontinuation time has elapsed is determined again (S402). Through theoperation in S402 and S403, whether or not the discharging operation isperformed within the starting continuation time is determined.

In a case where it is determined that the discharging operation of theextraction device 6 is performed (determination of YES in S403), thenumber of times of discharging operation n is counted up (plus one time)(S404). When the counting-up of the number of times of dischargingoperation n is finished, processing returns to S402, and the processingdescribed above is repeated.

In a case where it is determined that the starting continuation time haselapsed (determination of YES in S402), the discharge air amount Md(t),which is the amount of air actually extracted, is calculated (S405).Specifically, in S405, the discharge air amount Md(t) is calculated bymultiplying the discharge amount D1 of a non-condensable gas in one timeof the discharging operation of the extraction device 6 by the number oftimes of discharging operation n.

Next, a correcting method for the control device 7 described above willbe described with reference to FIG. 5.

A flowchart shown in FIG. 5 is executed after the discharging operationof the extraction device 6 is all completed and the discharge air amountMd(t) is calculated. The flowchart shown in FIG. 5 is executed each timethe discharging operation of the extraction device 6 is completed.

First, whether or not a difference between the estimated total amount ofinfiltrated air M(t) and the discharge air amount Md(t) (absolute value)is equal to or larger than the predetermined amount β is determined(S501). In a case where the difference between the estimated totalamount of infiltrated air M(t) and the discharge air amount Md(t)(absolute value) is smaller than the predetermined amount β(determination of NO in S501), a correction constant is not updated(S502).

In a case where the difference between the estimated total amount ofinfiltrated air M(t) and the discharge air amount Md(t) (absolute value)is equal to or larger than the predetermined amount β (determination ofYES in S501), a correction constant according to the difference betweenthe estimated total amount of infiltrated air M(t) and the discharge airamount Md(t) is read from the storage unit 24 (S503). Then, the readcorrection constant is updated by being multiplied by the correctionconstant set up until then (S504).

Next, the discharging operation of a non-condensable gas by the controldevice 7 described above will be described with reference to FIGS. 6 and7. FIG. 6 is a graph showing the amount of a non-condensable gas in thecondenser 3 of the chiller 1 according to the embodiment. FIG. 7 is agraph showing the amount of a non-condensable gas in the extractiondevice 6 of the chiller 1 according to the embodiment.

As shown in FIG. 6, the non-condensable gas accumulates in the chiller 1according to an operation state of the chiller 1 and externalenvironments. The amount of the non-condensable gas that is beingaccumulated is estimated by the estimating unit 21, and is accuratelyestimated as the correcting unit 26 performs correction. Then, in a casewhere the amount of the non-condensable gas accumulated in the condenser3 (the total amount of infiltrated air M(t)) exceeds the allowable valueMc, the extraction device 6 is started, and the non-condensable gasaccumulated in the condenser 3 is pulled out by the extraction device 6.

As shown in FIG. 7, in a case where the amount of the non-condensablegas accumulated in the condenser 3 (the total amount of infiltrated airM(t)) exceeds the allowable value Mc, the extraction device 6 isstarted, and the non-condensable gas is pulled out from the condenser 3.For this reason, the non-condensable gas accumulates in the extractiondevice 6. Then, in a case where the non-condensable gas accumulated inthe extraction device 6 reaches the predetermined discharge amount D1,the valve 9 is closed, and the non-condensable gas is discharged intothe atmosphere by the pump 11. Through the discharging operation, mostof the non-condensable gas accumulated in the extraction device 6 isdischarged. Then, as the valve 9 is opened again, the non-condensablegas is pulled out from the condenser 3 to the extraction device 6, andthe non-condensable gas accumulates in the extraction device 6. Then,the discharging operation is repeatedly performed as described above.Although a case where the discharging operation is performed two timesby the extraction device 6 in order to discharge the entirenon-condensable gas accumulated in the condenser 3 is described in anexample shown in FIG. 7, the invention is not limited to the example.

Although the correcting unit 26 calculates the air infiltration amountMa(s) by correcting the air infiltration amount M(s) of each sectionestimated by the estimating unit 21 and the estimating unit 21calculates a value by adding up the air infiltration amounts Ma(s), avalue to be corrected by the correcting unit 26 is not limited to theair infiltration amount M(s) of each section estimated by the estimatingunit 21. For example, when the estimating unit 21 estimates the airinfiltration amount M(s) of each section, a value obtained by adding upthe air infiltration amounts M(s) of respective sections (the airinfiltration amount Ms(s)) is calculated. Then, the correcting unit 26may correct the value obtained by adding up the air infiltration amountsM(s) of the respective sections (the air infiltration amount Ms(s)).Specifically, the correcting unit 26 corrects the air infiltrationamount Ms(s) by multiplying the value obtained by adding up the airinfiltration amounts M(s) of the respective sections estimated by theestimating unit 21 (the air infiltration amount Ms(s)) by the correctionconstant, and calculates the total amount of infiltrated air M(t) byadding the previously integrated value M(t−1) of air infiltrationamounts to the value. Whether or not the total amount of infiltrated airM(t) calculated in such a manner is equal to or larger than theallowable value Mc set in advance is determined by the determinationunit 22.

Next, a modification example of a correction target in the embodimentwill be described. Although a total amount of infiltrated air iscorrected in the first embodiment, instead of the correction of thetotal amount of infiltrated air or in addition to the correction of thetotal amount of infiltrated air, a starting continuation time set by thestarting control unit 23 is corrected in the modification example. Sincethe starting continuation time is determined by the total amount ofinfiltrated air M(t), the total amount of infiltrated air M(t) isindirectly corrected even when the starting continuation time iscorrected.

In the modification example, the storage unit 24 stores a table, inwhich a difference between the estimated total amount of infiltrated airM(t) and the discharge air amount Md(t) and a correction constant c′ forcorrecting a starting continuation time are set to correspond to eachother. Specifically, in a case where the correction necessitydetermination unit 31 determines that it is necessary to correct thetotal amount of infiltrated air M(t), the correction constant updatingunit 32 reads the correction constant c′ for correcting a startingcontinuation time according to the difference between the estimatedtotal amount of infiltrated air M(t) and the discharge air amount Md(t)from the storage unit 24, and updates the read correction constant bysetting as a new correction constant. Then, the correction executingunit 33 performs correction by multiplying the starting continuationtime by the new correction constant.

Next, a modification example of a correction constant in the embodimentwill be described. In a case where an air infiltration effect degree isset for each section and the correcting unit 26 corrects a total amountof infiltrated air, an air infiltration amount is corrected for eachsection according to an air infiltration effect degree in themodification example.

For this reason, in the modification example, the storage unit 24 storesan addition constant corresponding to an air infiltration effect degreeof each section. The correction executing unit 33 calculates the airinfiltration amount Ma(s) by multiplying the air infiltration amountM(s) of each section estimated by the estimating unit 21 by a correctionconstant and adding the addition constant corresponding to each section.In a case where the correction constant updating unit 32 does not updatethe correction constant (a case of c=1), the addition constant is notadded.

In consideration of an air infiltration effect degree of each section,the addition constant allows more effective correction. For this reason,the addition constant is set in advance through experiments according toan air infiltration effect degree.

For this reason, since the air infiltration amount M(s) of each sectionis corrected in consideration of an air infiltration effect degree ofeach section in the modification example, the air infiltration amountM(s) of each section can be more accurately corrected. That is, thetotal amount of infiltrated air M(t) calculated from the airinfiltration amount M(s) of each section can also be more accuratelycorrected.

Although the correcting unit 26 (the correction executing unit 33)corrects the air infiltration amount M(s) of each section (calculatesthe air infiltration amount Ma(s)) by multiplying the air infiltrationamount M(s) of each section estimated by the estimating unit 21 by acorrection constant and adding an addition constant corresponding toeach section in the modification example, correction performed by thecorrecting unit 26 is not limited to the description above. For example,first, the correcting unit 26 corrects the air infiltration amount M(s)of each section (weighting) by adding an addition constant correspondingto each section to the air infiltration amount M(s) of each sectionestimated by the estimating unit 21. Then, the correcting unit 26 maycorrect (calculate the air infiltration amount Ma(s)) by multiplying atotal value of the corrected air infiltration amounts M(s) forrespective sections by a correction constant. That is, the correctingunit 26 may correct (multiplication of a correction constant) the airinfiltration amount M(s) estimated for each section after weighting(addition of an addition constant) is performed according to an airinfiltration effect degree.

In the control device and the control method for an extraction deviceaccording to the embodiment as described above, the amount of anon-condensable gas infiltrated in the chiller 1 is estimated as a totalamount of infiltrated air, and the estimated total amount of infiltratedair and/or a starting continuation time of the extraction device 6 iscorrected based on a discharge air amount, which is the amount of airactually discharged by the extraction device 6. For this reason,according to an actual operation status of the chiller 1, the airinfiltration amount and the starting continuation time of the extractiondevice 6 can be appropriately corrected. Since the starting continuationtime of the extraction device 6 depends on an air infiltration amount,the total amount of infiltrated air is indirectly corrected even in acase of correcting the starting continuation time. That is, it ispossible to more accurately estimate a total amount of infiltrated airaccording to an operation status. For example, even in a case where alow-GWP refrigerant is used as a refrigerant of the chiller 1, it ispossible to more accurately estimate an air infiltration amount. Thus,more stable operation can be maintained. Since an air infiltrationamount can be more accurately estimated, the start of the extractiondevice 6 is optimized, and thus unnecessary power consumption can besuppressed.

Further, since correction is performed with simple calculation ofmultiplying an air infiltration amount and/or a starting continuationtime by a correction constant, correction can be performed without aprocessing burden.

Second Embodiment

Next, a control device and a control method for an extraction deviceaccording to a second embodiment of the present invention will bedescribed.

Although an air infiltration amount is estimated for each section in thefirst embodiment described above, the embodiment is different in thatthe total amount of infiltrated air M(t) of the entire chiller 1 isdirectly estimated without performing division into sections. That is,the chiller 1 in the embodiment is different from the first embodimentin terms of a calculation method of the total amount of infiltrated airM(t) by the estimating unit 21. Hereinafter, points of the chiller 1according to the embodiment, which are different from the firstembodiment, will be mainly described.

The estimating unit 21 according to the embodiment calculates thecurrent total amount of infiltrated air M(t) with the use of Expression(7) below.

M(t)=f(Mb×f(Ec′/Vc)×f(Pet, Pct))+M(t−1)   (7)

In Expression (7), Mb is an air infiltration amount of a referencechiller, f(Ec′/Vc) is a function having an air infiltration effectdegree and an in-chiller volume as parameters, Ec′ is an air effectdegree of the entire chiller 1 relatively determined based on astructural difference from the reference chiller, Vc is an in-chillervolume, and f(Pet, Pct) is a function having an evaporation pressure Petand a condensation pressure Pct as parameters. That is,Mb×f(Ec′/Vc)×f(Pet, Pct) in Expression (7) indicates the amount of airestimated to be infiltrated in the entire chiller 1 per unit time (perone control cycle). f(Mb×f(Ec′/Vc)×f(Pet, Pct)) is a function havingMb×f(Ec′/Vc)×f(Pet, Pct) as a parameter. Specifically,f(Mb×f(Ec′/Vc)×f(Pet, Pct)) indicates correction of the amount of airestimated to be infiltrated in the entire chiller 1 (Mb×f(Ec′/Vc)×f(Pet,Pct)).

As shown in Expression (7), the current total amount of infiltrated airM(t) is calculated by adding the previously integrated value M(t−1) ofair infiltration amounts to a value obtained by correcting the amount ofair estimated to be infiltrated in the entire chiller 1(Mb×f(Ec′/Vc)×f(Pet, Pct)).

Herein, the function (Ec′/Vc) having an air infiltration effect degreeand an in-chiller volume as parameters functions as a coefficientrelatively indicating the easiness of air infiltration in a structuralaspect. That is, the higher a value of the function, the more easily airinfiltrates from a structure surface than the reference chiller. Thefunction f(Pet, Pct) of an evaporation temperature and a condensationtemperature functions as a coefficient indicating the easiness of airinfiltration from a perspective of a pressure (a differential pressurebetween a pressure and the atmospheric pressure). That is, the lower apressure of the evaporator 5 and a pressure of the condenser 3, the moreeasily air infiltrates. Therefore, the higher the function value, themore easily air infiltrates from a perspective of a pressure.

The storage unit 24 in the embodiment stores a correction constant c″based on a difference between the estimated total amount of infiltratedair M(t) and the discharge air amount Md(t), which is for correcting theamount of air estimated to be infiltrated in the entire chiller 1(Mb×f(Ec′/Vc)×f(Pet, Pct)). The correcting unit performs correction bymultiplying Mb×f(Ec′/Vc)×f(Pet, Pct) in Expression (7) by the correctionconstant c″. That is, specifically, f(Mb×f(Ec′/Vc)×f(Pet, Pct))indicates multiplying Mb×f(Ec′/Vc)×f(Pet, Pct) by the correctionconstant c″. The determination unit 22 compares the total amount ofinfiltrated air M(t) calculated through Expression (7) and the allowablevalue Mc with each other.

In the control device 7 and the control method for the extraction device6 of the chiller 1 according to the embodiment, it is possible to reducea processing burden when calculating an air infiltration amount since itis not necessary to perform division into respective sections as in thefirst embodiment. Further, since a value relatively determined from astructural difference from the reference chiller is used also for an airinfiltration effect degree, it is possible to reduce an effort thattakes when determining an air infiltration effect degree. Then, sincethe total amount of infiltrated air M(t) estimated by the estimatingunit 21 is corrected based on a discharge air amount, it is possible tomore accurately estimate the amount of a non-condensable gas infiltratedin the chiller 1.

The present invention is not limited to only the embodiments describedabove, and it is possible to execute various modifications withoutdeparting from the gist of the invention.

For example, although a case where the control device 7 of the chiller 1has a function of controlling the extraction device 6 is described ineach of the embodiments, without being limited to this example, forexample, a control device dedicated for the extraction device 6 may beseparately provided with the control function of the extraction device 6separated from the control device 7.

Although the extraction device 6 is connected to the condenser 3 by thepipe 8 in each of the embodiments, the extraction device may beconnected to a place by other pipes insofar as air stays easily in theplace, in addition to the condenser 3. By connecting the place where airstays easily and the extraction device 6 to each other as describedabove, it is possible to efficiently discharge air in the device.

Further, although the extraction device 6 is started based on an airinfiltration amount in each of the embodiments, there is a possibilitythat a refrigerant is adversely affected by other substances such asmoisture. Therefore, infiltration amounts of other substances such asmoisture are estimated in addition to the air infiltration amount, andthe start and stop of means of removing or reducing the substancesaccording to the estimated infiltration amounts may be controlled. Aconfiguration where a structure that can remove other substances at alltimes (moisture removal by a filter dryer) is provided and othersubstances are removed at all times may be adopted.

REFERENCE SIGNS LIST

1: chiller

2: compressor

3: condenser

4: expansion valve

5: evaporator

6: extraction device

7: control device

8, 13: pipe

9, 12: valve

10: check valve

11: pump

14: pressure sensor

15: temperature sensor

16: extraction tank

21: estimating unit

22: determination unit

23: starting control unit

24: storage unit

25: discharge air amount calculating unit

26: correcting unit

31: correction necessity determination unit

32: correction constant updating unit

33: correction executing unit

1. A control device that controls an extraction device provided in achiller, the control device comprising: an estimating unit thatestimates a total amount of infiltrated air into the chiller; adetermination unit that determines whether or not the total amount ofinfiltrated air is equal to or larger than an allowable value set inadvance; a starting control unit that determines a starting continuationtime of the extraction device based on the total amount of infiltratedair and starts the extraction device for the starting continuation timein a case where the total amount of infiltrated air is equal to orlarger than the allowable value; a discharge air amount calculating unitthat calculates a discharge air amount, which is an amount of airactually discharged by the extraction device; and a correcting unit thatcorrects at least any one of the total amount of infiltrated air and thestarting continuation time in a case where a difference between thetotal amount of infiltrated air and the discharge air amount is equal toor larger than a predetermined amount.
 2. The control device accordingto claim 1, wherein the correcting unit corrects at least any one of thetotal amount of infiltrated air and the starting continuation time bymultiplying the total amount of infiltrated air or the startingcontinuation time by a correction constant according to the differencebetween the total amount of infiltrated air estimated by the estimatingunit and the discharge air amount.
 3. The control device according toclaim 2, wherein the correction constant is a value obtained by dividingthe discharge air amount by the total amount of infiltrated air.
 4. Thecontrol device according to claim 1, wherein the chiller is divided intoa plurality of sections, an air infiltration effect degree is set foreach of the sections, the estimating unit estimates an air infiltrationamount for each of the sections and estimates the total amount ofinfiltrated air of the entire chiller from the estimated airinfiltration amount of each of the sections, and the correcting unitcorrects the air infiltration amount for each of the sections accordingto the air infiltration effect degree in a case of correcting the totalamount of infiltrated air.
 5. A chiller that adopts a low-pressurelow-GWP refrigerant, the chiller comprising: an extraction device; andthe control device according to claim
 1. 6. A control method for anextraction device provided in a chiller, the control method comprising:an estimation step of estimating a total amount of infiltrated air intothe chiller; a determination step of determining whether or not thetotal amount of infiltrated air is equal to or larger than an allowablevalue set in advance; a starting control step of determining a startingcontinuation time of the extraction device based on the total amount ofinfiltrated air and starting the extraction device for the startingcontinuation time in a case where the total amount of infiltrated air isequal to or larger than the allowable value; a discharge air amountcalculation step of calculating a discharge air amount, which is anamount of air actually discharged by the extraction device; and acorrection step of correcting at least any one of the total amount ofinfiltrated air and the starting continuation time in a case where adifference between the total amount of infiltrated air and the dischargeair amount is equal to or larger than a predetermined amount.
 7. Achiller that adopts a low-pressure low-GWP refrigerant, the chillercomprising: an extraction device; and the control device according toclaim
 2. 8. A chiller that adopts a low-pressure low-GWP refrigerant,the chiller comprising: an extraction device; and the control deviceaccording to claim
 3. 9. A chiller that adopts a low-pressure low-GWPrefrigerant, the chiller comprising: an extraction device; and thecontrol device according to claim 4.